The TL431, A, B integrated circuits are three−terminal programmable shunt regulator diodes. These monolithic IC voltage references operate as a low temperature coefficient zener which is programmable from Vref to 36 V with two external resistors.
   
Features
• Programmable Output Voltage to 36 V
• Voltage Reference Tolerance: ±0.4%, Typ @ 25°C (TL431B)
• Low Dynamic Output Impedance, 0.22Ω Typical
• Sink Current Capability of 1.0 mA to 100 mA
• Equivalent Full−Range Temperature Coefficient of 50 ppm/°C Typical
• Temperature Compensated for Operation over Full Rated Operating
    Temperature Range
• Low Output Noise Voltage
• Pb−Free Packages are Available